This device relates to use of dispensers for studies requiring careful measurement of intake by animals. Many studies such as those investigating meal pattern, calorie intake, diet restriction and resultant metabolism require food intake measurements. In the case of animal models, food intake can be measured with varying levels of accuracy and sophistication and twenty-four hour intake is generally considered to be a good time period. For mouse models, for example, intake is often measured using group cages yielding an estimate of average intake per mouse as a gross measure that can provide meaningful information for some purposes. In many cases, twenty-four hour intake may simply be measured as the weight difference between food put into the cage and food remaining at the end of the 24-hour period. However, the accuracy of this method is limited by inability to account for gnaw waste, which is often a significant proportion of the difference between pre- and post- food weights, since the waste may fall on the bottom of the cage. Moreover, mice will often remove small pellets from a food hopper (food bin) and deposit them inside the cage where they combine with bedding, urine and feces. This food often can not be retrieved and isolated for measurement. Use of ground chow will prevent hoarding of food, but increases spillage. Combining the ground chow with water can reduce spillage but this changes the texture and palatability of the diet, which may induce altered food intake.
There are a number of systems available for tracking food intake in rodents. The simplest computer-based system employs a photocell, providing information about the feeding pattern but no quantitative consumption data. Other systems that provide both quantitative and feeding pattern data are quite expensive and difficult to maintain. Pellet dispensers that are less expensive are available with a variety of options. Traditional lever press systems serve mainly as measures of food motivation. More recent pellet systems linking food hoppers with infrared detectors provide mostly information about meal patterns with limited quantification of food intake. A major disadvantage many of these systems is clogging due to crumb accumulation. Therefore, the equipment must be frequently checked and cleaned. Pellet dispensers also limit the variety of diets that can be investigated and each pellet dispenser can generally deliver only one pellet size.